The present invention relates to a method for aligning optical fibers with a waveguide element; and, more particularly, to a method for aligning an optical fiber with a corresponding waveguide of the waveguide element by forming a groove for inserting the optical fiber into the waveguide element, instead of aligning an optical fiber with a waveguide by using an optical fiber block as known in the prior art.
One of the points at issue in producing waveguide elements is how to develop a simple method for aligning an optical fiber with a waveguide of the waveguide elements, and many researchers have focused on developing a packaging method insensitive to environmental and mechanical factors.
FIG. 1 illustrates a method for actively aligning an optical fiber with a waveguide, which is generally known in the prior art.
As shown in FIG. 1, optical fiber blocks 3 and 3a are arranged on both sides of a waveguide element 1, and the optical fiber blocks 3 and 3a are aligned with the waveguide element 1 by measuring the intensity of light passing through the waveguide.
One problem of the above mentioned method is that it takes excessive time to align the optical fiber blocks with the waveguide element due to the structural precision error of the waveguide element and the optical fiber blocks. Another problem is that although the waveguide element 1 and the optical fiber blocks 3 and 3a are precisely aligned, its characteristic can be changed due to mechanical and environmental factors.
Further problem arises from the fact that the optical fiber blocks 3 and 3a should be cut to make inclines 4 and 4a at an angle of equal to or more than 8 degrees in order to improve reflection characteristics. In this case, it takes excessive time to align the inclines 4 and 4a, and because it is impossible to polish consistently all of the inclines, the curvature radius of each waveguide is different from each other, so that it is difficult to attach the optical fiber blocks 3 and 3a to the waveguide element 1 in an optimal condition.
Further when the inclines 4 and 4a are butted, the axes of the optical fiber blocks are misaligned with the waveguide element due to the shear stress caused by adhesive being hardened. That is, the displacement xcex4 due to the adhesive stress between the inclines being butted is,
xcex4(deviation)=xcfx80dxcfx84/2G
where d is the thickness of the adhesive, xcfx84 is a shear stress, and G is a shear modulus of the adhesive.
As shown in the above equation, the displacement of 1 xcexcm results in the loss of 1.8 dB, and when the thickness of the adhesive is reduced, the inclines butted can easily come apart by any mechanical shock.
Another way to align an optical fiber with a waveguide is to insert a thin lens or film made of photosensitive material between the optical fiber and the waveguide. This approach is advantageous in that it is easy to align the optical fiber with the waveguide, and insensitive to the environmental factors. However, this approach has a problem in that the process of manufacturing photosensitive material is difficult, manufacturing cost is high, and optical coupling loss is increased due to the addition of one medium.
It is, therefore, an object of the present invention to provide a method for aligning an optical fiber with a waveguide, which is insensitive to the environmental and mechanical factors and cost effective.
In accordance with the present invention, there is provided a method for aligning optical fibers with a waveguide element, comprising the steps of: scanning a light source of visible broadband on one side of the waveguide element; capturing an image of the light, which is passing through waveguides in the waveguide element, projected on the other side of the waveguide element; processing the image to convert it into analysis data and storing the analysis data into a computer; forming grooves on one side of the waveguide element, wherein the axes of the grooves are aligned with the axes of the waveguides in accordance with the analysis data; and inserting the optical fibers into the grooves.